As a technology which compensates for waveform distortion in signal transmission in wireless communication and cable communication, a frequency domain equalization (FDE) technology is known. In FDE, first, a signal data in the time domain is converted to data in the frequency domain by Fast Fourier Transform (FFT). Then filter processing for equalization is performed and the signal data in the frequency domain is reconverted to the signal data in the time domain by Inverse FFT (IFFT). In FDE, by the above-mentioned processing, the waveform distortion of the signal is compensated for.
Meanwhile, in FFT, it is assumed that a signal repeats periodically, it is a problem that a computation distortion occurs in a signal around both ends of a processing block of FFT. As a technology which solves this problem, for example, an overlap FDE method disclosed in patent documents 1, 2 and 3 can be mentioned. In the overlap FDE method, FFT processing is performed by giving an overlap of a predetermined data between adjacent processing blocks, and then after performing filter processing and reconverting to a time domain signal by IFFT processing, only the signal data of the both ends of the processing block in which the computation-distortion occurs is removed.
As the other related arts, a digital filter device, described in patent document 4, which changes the sampling period of digital data is mentioned.